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Expose the kernel's build-ID through sysctl

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After our migration (of certain architectures) to lld the kernel is built
with a unique build-ID.  Make it available via a sysctl and uname(1) to
allow the user to identify their running kernel.

Submitted by:	Ali Mashtizadeh <ali_mashtizadeh.com>
MFC after:	2 weeks
Relnotes:	Yes
Event:		Waterloo Hackathon 2019
Differential Revision:	https://reviews.freebsd.org/D20326
This commit is contained in:
emaste 2019-06-04 13:07:10 +00:00
parent 01b5874679
commit 7236018555
14 changed files with 114 additions and 0 deletions
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5
sys/conf/ldscript.amd64
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@ -74,6 +74,11 @@ SECTIONS
PROVIDE (etext = .);
.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.eh_frame_hdr : { *(.eh_frame_hdr) }
.eh_frame : ONLY_IF_RO { KEEP (*(.eh_frame)) }
.gcc_except_table : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }

5
sys/conf/ldscript.arm
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@ -27,6 +27,11 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.rel.text :
{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
.rela.text :

5
sys/conf/ldscript.arm64
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@ -27,6 +27,11 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.rel.text :
{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
.rela.text :

5
sys/conf/ldscript.i386
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@ -62,6 +62,11 @@ SECTIONS
PROVIDE (etext = .);
.rodata : { *(.rodata .rodata.* .gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.eh_frame_hdr : { *(.eh_frame_hdr) }
.eh_frame : ONLY_IF_RO { KEEP (*(.eh_frame)) }
.gcc_except_table : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }

5
sys/conf/ldscript.mips
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@ -63,6 +63,11 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.rel.init : { *(.rel.init) }
.rela.init : { *(.rela.init) }
.rel.text :

5
sys/conf/ldscript.mips.cfe
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@ -192,6 +192,11 @@ SECTIONS
PROVIDE (etext = .);
.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.reginfo : { *(.reginfo) }
.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }

5
sys/conf/ldscript.mips.mips64
View File

@ -176,6 +176,11 @@ SECTIONS
PROVIDE (etext = .);
.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.reginfo : { *(.reginfo) }
.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }

6
sys/conf/ldscript.mips.octeon1
View File

@ -23,6 +23,12 @@ SECTIONS {
*(.rodata)
. = ALIGN(32);
}
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.data : {
_rwdata = .;

5
sys/conf/ldscript.powerpc
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@ -55,6 +55,11 @@ SECTIONS
.fini : { *(.fini) } =0
.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.sdata2 : { *(.sdata2) }
.sbss2 : { *(.sbss2) }
/* Adjust the address for the data segment to the next page up. */

5
sys/conf/ldscript.powerpc64
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@ -46,6 +46,11 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.rela.text :
{ *(.rela.text) *(.rela.gnu.linkonce.t*) }
.rela.data :

5
sys/conf/ldscript.powerpcspe
View File

@ -55,6 +55,11 @@ SECTIONS
.fini : { *(.fini) } =0
.rodata : { *(.rodata) *(.gnu.linkonce.r*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.sdata2 : { *(.sdata2) }
.sbss2 : { *(.sbss2) }
/* Adjust the address for the data segment to the next page up. */

5
sys/conf/ldscript.riscv
View File

@ -27,6 +27,11 @@ SECTIONS
.gnu.version : { *(.gnu.version) }
.gnu.version_d : { *(.gnu.version_d) }
.gnu.version_r : { *(.gnu.version_r) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.rel.text :
{ *(.rel.text) *(.rel.gnu.linkonce.t*) }
.rela.text :

5
sys/conf/ldscript.sparc64
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@ -146,6 +146,11 @@ SECTIONS
PROVIDE (etext = .);
.rodata : { *(.rodata) *(.rodata.*) *(.gnu.linkonce.r.*) }
.rodata1 : { *(.rodata1) }
.note.gnu.build-id : {
PROVIDE (__build_id_start = .);
*(.note.gnu.build-id)
PROVIDE (__build_id_end = .);
}
.sdata2 : { *(.sdata2) *(.sdata2.*) *(.gnu.linkonce.s2.*) }
.sbss2 : { *(.sbss2) *(.sbss2.*) *(.gnu.linkonce.sb2.*) }
. = ALIGN(0x2000) + (. & (0x2000 - 1));

48
sys/kern/kern_mib.c
View File

@ -481,6 +481,54 @@ SYSCTL_PROC(_kern, KERN_OSRELDATE, osreldate,
CTLTYPE_INT | CTLFLAG_CAPRD | CTLFLAG_RD | CTLFLAG_MPSAFE,
NULL, 0, sysctl_osreldate, "I", "Kernel release date");
/*
* The build-id is copied from the ELF section .note.gnu.build-id. The linker
* script defines two variables to expose the beginning and end. LLVM
* currently uses a SHA-1 hash, but other formats can be supported by checking
* the length of the section.
*/
extern char __build_id_start[];
extern char __build_id_end[];
#define BUILD_ID_HEADER_LEN 0x10
#define BUILD_ID_HASH_MAXLEN 0x14
static int
sysctl_build_id(SYSCTL_HANDLER_ARGS)
{
uintptr_t sectionlen = (uintptr_t)(__build_id_end - __build_id_start);
int hashlen;
char buf[2*BUILD_ID_HASH_MAXLEN+1];
/*
* The ELF note section has a four byte length for the vendor name,
* four byte length for the value, and a four byte vendor specific
* type. The name for the build id is "GNU\0". We skip the first 16
* bytes to read the build hash. We will return the remaining bytes up
* to 20 (SHA-1) hash size. If the hash happens to be a custom number
* of bytes we will pad the value with zeros, as the section should be
* four byte aligned.
*/
if (sectionlen <= BUILD_ID_HEADER_LEN ||
sectionlen > (BUILD_ID_HEADER_LEN + BUILD_ID_HASH_MAXLEN)) {
return (ENOENT);
}
hashlen = sectionlen - BUILD_ID_HEADER_LEN;
for (int i = 0; i < hashlen; i++) {
uint8_t c = __build_id_start[i+BUILD_ID_HEADER_LEN];
snprintf(&buf[2*i], 3, "%02x", c);
}
return (SYSCTL_OUT(req, buf, strlen(buf) + 1));
}
SYSCTL_PROC(_kern, OID_AUTO, build_id,
CTLTYPE_STRING | CTLFLAG_CAPRD | CTLFLAG_RD | CTLFLAG_MPSAFE,
NULL, 0, sysctl_build_id, "A", "Operating system build-id");
SYSCTL_NODE(_kern, OID_AUTO, features, CTLFLAG_RD, 0, "Kernel Features");
#ifdef COMPAT_FREEBSD4